Automotive engineers and designers have long sought to create vehicles having aesthetically pleasing exterior and interior designs. Exterior designs have become increasingly uniform over the years. Hence, the importance of uniqueness and aesthetic appeal in the automotive interior has grown. Attractive upholstered coverings for interior trim, seats, and steering wheels are a hallmark of the modern, high quality automobile. Ever-high customer quality demands continue to raise the bar for commercial acceptability, and aesthetic appeal has become paramount in the sale of higher profit margin vehicles. Accordingly, attention has turned to a less traditional element of interior design.
One example of such new focus involves the appearance of seams in upholstered interior components such as seats, headrests, instrument panel pads and the like. Many leather and vinyl top layers of automotive interior parts have simulated exterior stitching that is molded integrally therein. This kind of simulated stitching can only have limited visual similarity to functional stitching, since it necessarily has the same color and appearance as the vinyl top layer with which it is integrally molded. Many current prior art interior surfaces now have a decorative stitching provided by real thread which require visual loops that lay flat on and tensioned against the top layer of the trim part for a desirable appearance and so as to not be pulled out of the trim part during ordinary use of the vehicle. The thread of these prior art seams which form the stitching have relatively thin, tough and incompressible characteristics so as to both properly visually stimulate functional stitching and as to stand up to wear on the surface of the trim part.
One type of prior art seam that is used on many automotive vehicle interior components including seats is a french seam that presents a clean appearance for a joint which joins two pieces of material of a seat together at a secured seam. Prior art french seams are made by applying a foam material to the back side of the leather, vinyl or other types of upholstery by laminating the foam to the back of the upholstery to ensure that the foam is secured to the material. One portion of a first material is then sewn to a portion of the second material. Then the edges are flipped over each other and a seam is placed a predetermined distance from the joint seam to create a french seam look. The french seam gets the appearance from the foam being compressed on itself creating a hump like appearance adjacent to the seam thus creating the french seam look that is desired by many automobile manufacturers.
The creation of a french seam in the prior art is very costly and labor intensive because the foam material has to be laminated to the back side of the material or other components to create the french seam. This reduces productivity and increases the cost of manufacturing the materials for these interior components. Furthermore, the creation of the french seam is complicated and time consuming because of the laminating of the foam to the back of the material. Also the french seam of many prior art materials do not have uniform humps along the entire french seam and create a less than desirable appearance for the french seam in many instances.
Therefore, there is a need in the art for an improved french seam that reduces the cost, is stronger, creates a cleaner and more aesthetically pleasing seam and is easier to manufacture into automotive interior materials.